TV booster off lighting circuit

[Brucie]

I have a tv signal splitter and booster wired into my lighting circuit in the loft (that is the only electrical circuit in the loft). The setup is a junction box running of the light main then through a switched fuse then the booster and splitter wired into another junction box. My problem is that when I switch on the light in the room underneath, the booster/splitter turn off. I know there is power still going into them because my electricity detector bleeps when it touches the cable after the switched fuse.
Is it possible that there is only enough current to run either the light or the boosters from the junction?
If so can I run another cable from the lighting main to the junction box before the switched fuse so the setup can pull power from two sources?
Or would I be better running the splitter off one junction box and the booster off another junction box further round the lighting main?

Sorry if it sounds complicated but this is the best way I seem to be ablte to explain my setup.
Please advise.
John

 

[Adam_151]

You haven't done anything daft like paralleled the booaster across the switch contacts have you?

 

[Brucie]

Not that I am aware of. I followed the same layout as a fan I have running off the downstairs lighting circuit. That works ok so I thought this would?
What am I looking for in the cabling to check for paralling?

 

[Adam_151]

switch the power off, put your multimeter on continuity across the supply to the booster, try the switch in both positions, post back what you get

 

[ibruceuk]

To me it sounds like you have wired the booster into a permanent live and a switched live. Reason being, when the light is off the booster / splitter is getting it's live from the permanent live, but it's neutral is flowing through the bulb. When the light is on this 'neutral' becomes live and hence it doesn't work.

You need to move your neutral feed to a neutral in the junction box (not just a black wire). The black wire (I'm assuming here) is probably the switch return wire.

You could do with using a multimeter to check the cables you are connecting into.

 

[Brucie]

I got my hands on a multimeter this morning for this situation. silly question, how do I use it to check if I have tapped into the switched live cable? For information, the cable has only black, red and earth wire.

 

[Brucie]

I cut my losses. Gave in to my lack of knowledge. I hunted around the loft for another junction box and tapped into that. Now all is well. Thanks everyone for your advise